Bubble-assisted CVD construction of heterointerface-dense CuOx-SnO2/graphene catalyst for efficient alkaline HER

Developing earth-abundant cathodes that can simultaneously promote interfacial water dissociation and sustain rapid electron delivery remains a central challenge for the alkaline hydrogen evolution reaction (HER), because oxide-rich surfaces favorable for water activation are often limited by semiconducting charge transport. To address this challenge, we synthesized a graphene-supported CuOx-SnO2 hybrid catalyst via a bubble-assisted molten-metal chemical vapor deposition process, in which methane served as the carbon source, while molten Cu-Sn acted both as the catalytic medium for graphene growth and as the source of Cu/Sn-containing surface species. The resulting Sn-Cu@G/NF electrode features dense local CuO x -SnO 2 heterointerfaces embedded within a conductive graphene scaffold. With this integrated architecture, Sn-Cu@G/NF requires only 127.4 mV to reach 10 mA cm −2 in 1.0 M KOH under dark conditions, together with a Tafel slope of 88 mV dec −1 and a charge-transfer resistance of 1.88 Ω, markedly outperforming the physically mixed control electrodes, G/NF, and bare NF. HRTEM/FFT, Mott–Schottky, and Kelvin probe force microscopy analyses further indicate that dense local SnO 2 /CuO x heterointerfaces are associated with junction-like charge redistribution and built-in potentials that are likely to facilitate directional charge transfer during HER, demonstrating the promise of local oxide–oxide heterointerfaces within a conductive graphene-based electrode architecture for alkaline HER.